27 



The highly organised nitrogenous materials above mentioned, 

 in soils containing a good supply of phosphates, potash, carbonate 

 of lime, and air, moisture, and the right kinds of bacteria, are 

 first modified or digested into soluble peptones by a class of bac- 

 teria which secrete a peptonizing ferment. Bacillus tumescens, 

 Zopf, B. ellenbachiensis, Caron, B. mycoidcs, Fluegge, etc., are good 

 examples of this class. These peptonized products (peptones and 

 albumoses) are then converted into ammonia through the action of 

 these same species and other ammonifying bacteria. The ammonia 

 may then be converted into nitrate by another class of bacteria, 

 principally Nitromonas europae, widely distributed in Europe, and 

 by species of Nitrococcus, said to be peculiar to the soils of Ame- 

 rica and Australia.* The nitrate is then oxidized to nitrate by 

 still another kind of bacterium, Nitrobacter. 



On the other hand, if the soil is poorly aerated or deficient in 

 moisture, lime, or other mineral plant foods, the course of this 

 digestion or decay of organic matter is modified. Acids accu- 

 mulate, and the bacterial action is largely replaced by that of 

 fungi and forms of bacteria that can grow in the presence of 

 acids. The organic matter becomes more or less pickled or humi- 

 fied. The more active forms of peptonizing and ammonifying 

 bacteria and the nitrifying forms are suppressed by the conditions 

 unfavourable to their development. Peaty soils represent the 

 extreme of this type. In the improvement of such soils the 

 great stores ot nitrogen and carbon of the humus may be made 

 available by the addition of the mineral foods if they are lacking 

 — especially carbonate of lime or potash — by proper aeration, and 

 finally by the addition of the peptonizing, ammonifying and 

 nitrifying bacteria. In the present state of our knowledge the 

 last is best accomplished by spreading a few hundred pounds per 

 acre of good, naturally rich, well-worked loam, which usually con- 

 tains these bacteria. Care should be taken, however, to secure this 

 inoculating soil from fields known to be free from serious weeds, 

 insects, and plant-disease organisms. It is to be hoped that our 

 knowledge of soil bacteriology will develop in the near future 

 to the point where we will be able to determine by bacterial 

 analysis what organisms are present in a given soil, and what 

 bacteria are needed to raise the bacterial activity to the highest 

 state of efficiency, assuming of course that the proper conditions 

 lor their growth have been supplied. Briefly, these conditions 

 are a warm temperature, good aeration brought about by thorough 

 and frequent cultivation, proper moisture conditions, also favoured 

 by thorough and frequent cultivation, good drainage, and a good 

 supply of decaying organic matter, carbonate of lime, phos- 

 phates, and other mineral foods. 



The following table, taken from Bulletin 65 ot the Delaware 

 College Agricultural Experiment Station, by F. D. Chester, shows 

 the varying activity of some of the bacteria here under discus- 

 sion : — 



•Hall, Alfred D., The Soil, p. 72, 1903. 



